JP-A-2009-148121 teaches that charging of a battery mounted on a plug-in vehicle is performed by utilizing multiple power sources in ascending order according to a unit price of electricity. Further, a charging time of the solar photovoltaic generation, which has the cheapest unit price of electricity, is adjusted based on weather report.
In the above device, since the solar photovoltaic generation having the cheapest unit price of electricity is utilized at a maximum extent in order to charge the battery. Thus, the charging cost is reduced.
However, although an optimum charging plan to a next driving time is executed based on the weather forecast and information of the solar photovoltaic generation, even if a charging amount for the next driving is small, the charging is performed from a commercial power source in a time zone other than a solar photovoltaic generation time zone. In this case, the charging cost is not cheap.
Further, in the above case, the battery is charged with a low cost to the utmost extent until the next driving time. Thus, even when the necessary electric power for driving at the next time is charged in the battery, the battery may be charged excessively.